影响滤筒分析质量的主要因素和改进方法

介绍了影响滤筒称量恒重的原因,指出空气湿度、冷却时间和烘干时间等对滤筒称量恒重都有影响。提出使用标准空白滤筒、在平衡室中冷却、称量滤筒、并采用专用滤筒盒和刚玉滤筒采样减小系统误差。     

烟尘监测时采样滤筒的质量控制

介绍了合格滤筒的筛选方法和采样滤筒在实验室分析中的质量控制,分析了影响滤筒称量恒重的原因,指出空气湿度、冷却时间和烘干时间对滤筒称量恒重都有影响.     

烟尘监测中应注意滤筒的质量控制

在烟尘监测中,采用玻璃纤维滤筒收集烟尘,实验室进行滤筒称量时,受实验室环境湿度、冷却时间、烘干时间等因素的影响,对监测结果有显著的影响,且呈现正误差。引入标准空白滤筒的恒重控制分析称量过程,可以消除这些因素引起的误差,提高烟尘监测分析质量。     

烟尘滤筒称重方法的改进

针对在烟尘测试中滤筒的称重存在天平显示不稳、恒重难的现象进行了探讨。比较了2种称量方法，提出在平衡室中冷却、称量滤筒，并采用标准滤筒来减小由于称重条件不同而产生的系统误差。结果表明，改进方法具有称量稳定、易恒重、失重少的优势。     

氨法脱硫废气中烟尘测试方法的实验研究

利用重量法测试原理,将氨法脱硫外排废气中烟尘监测滤筒用二次水经过超声波洗涤后过滤,在烘箱内于105℃烘干2 h后称量恒重,除去滤简中的硫酸铵成分,从而准确获得烟尘的含量.     

快速、准确测定大气硫酸盐化速率的方法

1抽滤硫酸钡沉淀时应少液多洗 ,即用少量温水多次冲洗 ,直至滤液不含 Cl-为止。 2 Cl-检验方法 :抽滤后的坩埚底部往往存有一滴或几滴滤液 ,把这几滴滤液移到表皿上 ,加一滴 1 %硝酸银即可检验。 3坩埚应放在 1 2 0～ 1 30℃烘箱中 ,烘 1 .5小时 ,在干燥器中冷却至室温 (或 1小时 ) ,恒重率达 98%以上。 4建立每一坩埚的基本重量。每一坩埚在使用前应反复冲洗、浸洗、恒重 ,直至其重量不再减少 ,这时的重量作为此坩埚的基本重量。若坩埚重量与基本重量相差小于0 .8mg,就认为此坩埚冲洗干净。快速、准确测定大气硫酸盐化速率的方法@贾文仲$…     

水中悬浮物的测定要点

水中悬浮物的测定要点李凤莲（航天总公司０６７基地环境监测站，西安７１００００）经实验表明，①样品称量所用时间相同（７ｍｉｎ），而冷却时间不同（分别为４０、３０ｍｉｎ），则两次称量最小误差０７ｍｇ，最大误差２３ｍｇ，５次称量无一样品达到恒重。②冷却...     

烟尘测试中滤筒称重问题

烟尘测试中滤筒称重问题张萍萍（福建龙岩地区环境监测站，龙岩３６４０００）①当滤筒放入天平称重时，滤筒湿度较天平内空气湿度小，产生吸湿现象，天平显示不稳。实验表明，最初称量的５个滤筒应放回干燥器内重新干燥、重新称量。②干燥时间的确定：实验表明，在内径为...     

解决滤筒不粘压环的方法

方法 1 :将装好滤筒的采样管背向气流放在采样点上预热 5至 1 0 min,估计滤筒的温度大致上升到烟气温度 ,即可开始采样。这种方法虽好 ,但不足之处是 ,浪费的时间长。同时也增加了扶采样管的人的工作量。方法 2 :在安装滤筒前 ,用布将滤筒的压环和滤筒夹的口部 ,认真地擦几遍 ,直到擦试干净为止 ,即可装滤筒开始采样。这种方法较容易掌握 ,且操作简单 ,建议大家一试。解决滤筒不粘压环的方法@王启华$焦作市中州铝厂安环处!河南焦作454174     

不同滤筒中无机元素含量探讨

选择国内10家制造商的玻璃纤维滤筒和国外2家制造商的石英滤筒,分别测定空白滤筒中的铍、铬、铅等17种元素,探讨不同滤筒中各元素的含量分布,同时结合相关分析方法标准的质控要求,评价各制造商玻璃纤维滤筒在废气监测中的适用性。     

An evaluation of benthic macroinvertebrate biomass methodology

Evaluation of analytical methods employed for wet weight (live or preserved samples) of benthic macroinvertebrates reveals that centrifugation at 140 x gravity for one minute yields constant biomass estimates. Less relative centrifugal force increases chance of incomplete removal of body moisture and results in weighing error, while greater force may rupture fragile macroinvertebrates, such as mayflies. Duration of specimen exposure in ethanol, formalin, and formol (formaling-ethanol combinations) causes significant body weight loss with within 48 hr formalin and formol cause less body weight loss than ethanol. However, as all preservatives tested cause body weight loss, preservation time of samples collected for comparative purposes should be treated uniformly. Dry weight estimates of macroinvertebrates are not significantly affected by kind of preservative or duration of exposure. Constant dry weights are attained by oven drying at 103 °C at a minimum of four hours or vacuum oven drying (15 inches of mercury pressure) at 103 °C for a minimum of one hour. Although requiring more time in preparation than oven drying and inalterably changing specimen body shape, freeze drying (10 microns pressure, -55 °C, 24 hr) provides constant dry weights and is advantageous for long term sample storage by minimizing curatorial attention. Constant ash-free dry weights of macroinvertebrate samples are attained by igniting samples at 500–550 °C for a minimum of one hour with slow cooling to room temperature in desiccators before weighing.     

环境空气中挥发性有机物监测技术细化研究

真空罐/气相色谱-质谱法是我国目前用于环境空气中挥发性有机物（VOCs）监测的主要方法。对该方法的采样前及采样环节的技术细节（包括流量控制器和过滤器的校准检查,采样罐的性能检查,样品的采集、运输及保存）,以及实验室分析环节的技术细节（包括色谱柱的选择,内标物的选择,湿度及气体稀释仪对分析结果的影响,标准曲线绘制方式和系统性能优劣的判断）进行讨论和分析。并针对以上技术细节提出解决方案和注意事项,以期为分析人员提供技术参考。     

A comparison of sampling and analysis methods for low-ppbC levels of volatile organic compounds in ambient air

A carefully designed study was conducted during the summer of 1998 to collect samples of ambient air by canisters and compare the analysis results to direct sorbent preconcentration results taken at the time of sample collection. Thirty-two 1 h sample sets were taken, each composed of a "near-real-time" sample analyzed by an autoGC-MS XonTech 930/Varian Saturn 2000 system, and Summa and Silco canisters. Hourly total non-methane organic carbon (TNMOC), ozone, and meteorological measurements were also made. Each canister was analyzed on the autoGC-MS system for a target list of 108 volatile organic compounds (VOCs) and on a manual cryosampling GC-FID system. Comparisons were made between the collection and analysis methods. Because of the low sample loading (150-250 ppbC TNMOC), these comparisons were a stringent test of sample collection and analysis capabilities. The following specific conclusions may be drawn from this study. Reasonable precision (within 15% mean difference of duplicate analyses from the same canister) can be obtained for analyses of target VOCs at low-ppbC concentrations. Relative accuracy between the GC-MS and GC-FID analysis methods is excellent, as demonstrated by comparisons of analyses of the same canisters, if measurements are sufficiently above the detection limits. This is especially significant as the GC-MS and GC-FID were independently calibrated. While statistically significant differences may be observed between the results from canister and near-real-time samples, the differences were generally small and there were clear correlations between the canister results and the near-real-time results. Canister cleanliness limits detection below the EPA Method TO-14 acceptance standard of 0.2 ppbv (0.2-2 ppbC for target analytes).     

Development of a sampling train for arsenic in pyrolysis vapours resulting from pyrolysis of arsenic containing wood waste

In the present study a sampling and analysis method for arsenic emissions during pyrolysis of arsenic containing wood, such as chromated copper arsenate (CCA) treated wood, has been developed. The procedure is based on the NIOSH (National Institute for Occupational Safety and Health) standard for arsenic trioxide sampling. Validation for this specific application is needed since pyrolysis of arsenic containing wood leads to a gas stream containing sticky tar compounds and aerosols. Validation was carried out through tube furnace experiments using both CCA treated wood and arsenic trioxide powder as input. The outlet of the tube furnace was coupled to a cooling section and sampling train. The sampling train consisted of one or more filter sections and impingers. Different combinations of filters (untreated or impregnated) and impingers, as well as different combinations of washing solutions were tested. The different units of the sampling train were analysed by inductively coupled plasma mass spectrometry (ICP-MS) in order to determine the distribution of arsenic over the different units. For the working conditions considered (pyrolysis at 350 degrees C for 20 minutes with a nitrogen flow rate of 100 Nl h(-1)) the combination of a quartz cooling tube and a cellulose ester membrane filter impregnated with a Na2CO3-glycerol solution was sufficient to capture the arsenic. Two extra impingers (the first one containing 50 ml HNO3 1 M in the case of CCA treated wood and 50 ml NaOH 0.1 M in the case of As2O3 and the second one containing 50 ml NaOH 0.1 M) were added downstream of the filter section as backup either in case of filter failure or to check whether all the arsenic released is captured by the cooling tube and filter.     

Comparison of 24 h averaged VOC monitoring results for residential indoor and outdoor air using Carbopack X-filled diffusive samplers and active sampling--a pilot study

Analytical results obtained by thermal desorption GC/MS for 24 h diffusive sampling of 11 volatile organic compounds (VOCs) are compared with results of time-averaged active sampling at a known constant flow rate. Air samples were collected with co-located duplicate diffusive sampling tubes and one passivated canister. A total of eight multiple-component sampling events took place at fixed positions inside and outside three private homes. Subsequently, a known amount of sample air was transferred from the canister to an adsorbent tube for analysis by thermal desorption GC/MS. Results for the 11 most prevalent compounds--Freon 11, 1,3-butadiene, benzene, toluene, tetrachloroethene, ethylbenzene, m,p-xylene, o-xylene, 4-ethyltoluene, 1,3,5-trimethylbenzene, and p-dichlorobenzene--show that the ratio of average study values (diffusive sampling to active sampling) is 0.92 with 0.70 and 1.14 extreme ratios. Absolute percent difference for duplicate samples using diffusive sampling was <10% for the four most prevalent compounds. Agreement between the two sampling approaches indicates that the prediction of approximately constant diffusive sampling rates based on previous laboratory studies is valid under the field conditions.     

废气样品中甲烷的保存条件研究

气相色谱法检测废气中甲烷,样品保存容器可选择玻璃注射器、惰性气袋、真空瓶、苏码罐等,实验室对此做了比较研究。结果表明:玻璃注射器气密性较差,样品须在8 h内完成分析;真空瓶携带不方便,苏码罐价格昂贵,两者使用较少;使用玻璃注射器采集,然后注入惰性气袋保存的方法最佳,样品至少可稳定保存7d。     

空气中挥发性有机物污染状况及健康风险评价

为了了解南京某县空气中挥发性有机污染物(VOCs)的污染状况,采用苏码罐采样-气相色谱-质谱法分析了该县不同功能区空气中的VOCs,探讨了其可能来源并采用国际公认的评价模型,对空气中的VOCs进行了健康风险评价。